linux-kernel - Re: [PATCH v4 1/2] PCI: dwc: Always stop link in the dw_pcie_suspend

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Message-ID: <Z4a71nPa1H01+Ang@lizhi-Precision-Tower-5810>
Date: Tue, 14 Jan 2025 14:32:38 -0500
From: Frank Li <Frank.li@....com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Richard Zhu <hongxing.zhu@....com>, dlemoal@...nel.org,
	jingoohan1@...il.com, bhelgaas@...gle.com, lpieralisi@...nel.org,
	kw@...ux.com, manivannan.sadhasivam@...aro.org, robh@...nel.org,
	quic_krichai@...cinc.com, imx@...ts.linux.dev,
	kernel@...gutronix.de, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] PCI: dwc: Always stop link in the
 dw_pcie_suspend_noirq

On Tue, Jan 14, 2025 at 12:15:18PM -0600, Bjorn Helgaas wrote:
> On Tue, Dec 10, 2024 at 04:15:56PM +0800, Richard Zhu wrote:
> > On i.MX8QM, PCIe link can't be re-established again in
> > dw_pcie_resume_noirq(), if the LTSSM_EN bit is not cleared properly in
> > dw_pcie_suspend_noirq().
> >
> > Add dw_pcie_stop_link() into dw_pcie_suspend_noirq() to fix this issue and
> > keep symmetric in suspend/resume function since there is
> > dw_pcie_start_link() in dw_pcie_resume_noirq().
> >
> > Fixes: 4774faf854f5 ("PCI: dwc: Implement generic suspend/resume functionality")
> > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware-host.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> > index f882b11fd7b94..f56cb7b9e6f99 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> > @@ -1001,6 +1001,7 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
> >  		return ret;
> >  	}
> >
> > +	dw_pcie_stop_link(pci);
>
> We should try to avoid changes to the generic DWC path just to
> accommodate one controller.  Since other DWC-based controllers
> apparently don't need dw_pcie_stop_link() here, this seems like it
> might be the wrong place for this change.
>
> If doing dw_pcie_stop_link() here is really helpful for all DWC
> controllers, this would be fine, but the commit log should then explain
> why it helps everybody, not why one particular controller benefits.

It should be for all dwc controllers although find such problem at i.MX8QM
platfrom. It should keep symmetric between suspend/resume function.

So far only layerscape and i.MX platform use these common functions. Other
dwc platform still have not switched to this common function yet.

Frank

>
> If it's only needed for i.MX8QM, we do already have a
> controller-specific hook (.deinit()) just below; maybe that could be
> used?
>
> >  	if (pci->pp.ops->deinit)
> >  		pci->pp.ops->deinit(&pci->pp);
> >
> > --
> > 2.37.1
> >